Current wireless mobile communication devices include microprocessors, memory, soundcards, speakers, headphones, and run one or more software applications in addition to providing for voice communications. Examples of software applications used in these wireless devices include micro-browsers, address books, email clients, instant messaging (“IM”) clients, and wavetable instruments. Additionally, wireless devices have access to a plurality of services via the Internet. A wireless device may, for example, be used to browse web sites on the Internet, to transmit and receive graphics, and to execute streaming audio and/or video applications. Such wireless devices may operate on a cellular network, on a wireless local area network (“WLAN”), or on both of these types of networks.
One problem with current wireless devices pertains to the adjustment of maximum output sound pressure levels for headphones coupled to such devices. Headphones are typically used to listen to voice calls, radio programs, audio programs (e.g., music), etc., stored on or accessed by the wireless device. In particular, the maximum output sound pressure level for headphones for wireless devices and handheld products is legally constrained in several jurisdictions in order to protect users from hearing loss. For example, European Standard EN 50332-1:2000, dated March 2000 and entitled “Sound System Equipment: Headphones And Earphones Associated With Portable Audio Equipment—Maximum Sound Pressure Level Measurement Methodology And Limit Considerations—Part 1: General Method For ‘One Package Equipment’”, and which is incorporated herein by reference, restricts maximum sound pressure level at the headphones (i.e., for headphones provided with the portable audio equipment and from the same manufacturer) to 100 dB. In addition, European Standard EN 50332-2:2003, dated October 2003 and entitled “Sound System Equipment: Headphones And Earphones Associated With Portable Audio Equipment—Maximum Sound Pressure Level Measurement Methodology And Limit Considerations—Part 2: Matching Of Sets With Headphones If Either Or Both Are Offered Separately”, and which is incorporated herein by reference, restricts maximum sound pressure level at the headphones (i.e., for headphones provided separately from the portable audio equipment by a different manufacturer) to 94 dB. Measurement of maximum sound pressure levels according to these standards is specified with respect to headphones having an impedance of 32 Ohms. One problem relating to such standards is that in order to set the output signal level (e.g., in mV RMS) appropriately at the output jack of the wireless device in order to meet the maximum sound pressure level specified, the impedance of the headphones must be known. This is especially problematic if the headphones are not provided by the manufacturer as a package with the wireless device.
A need therefore exists for an improved method and system for controlling a maximum signal level output to headphones coupled to a wireless device. Accordingly, a solution that addresses, at least in part, the above and other shortcomings is desired.
It will be noted that throughout the appended drawings, like features are identified by like reference numerals.